Document Detail

Post-embryonic development of the Furongian (late Cambrian) trilobite Tsinania canens: implications for life mode and phylogeny.
MedLine Citation:
PMID:  19601977     Owner:  NLM     Status:  MEDLINE    
The current concept of the order Asaphida was proposed to accommodate some Cambrian and Ordovician trilobite clades that are characterized by the possession of a ventral median suture. The family Tsinaniidae was recently suggested to be a member of the order Asaphida on the basis of its close morphological similarity to Asaphidae. Postembryonic development of the tsinaniid trilobite, Tsinania canens, from the Furongian (late Cambrian) Hwajeol Formation of Korea, reveals that this trilobite had an adult-like protaspis. Notable morphological changes with growth comprise the effacement of dorsal furrows, sudden degeneration of pygidial spines, regression of genal spines, and loss of a triangular rostral plate to form a ventral median suture. Programmed cell death may be responsible for degenerating the pygidial and genal spines during ontogeny. Morphological changes with growth, such as the loss of pygidial spines, modification of pleural tips, and effacement of dorsal furrows, suggest that T. canens changed its life mode during ontogeny from benthic crawling to infaunal. The protaspid morphology and the immature morphology of T. canens retaining genal and pygidial spines suggest that tsinaniids bear a close affinity to leiostegioids of the order Corynexochida. Accordingly, development of a ventral median suture in T. canens demonstrates that the ventral median suture could have evolved polyphyletically, and thus the current concept of the order Asaphida needs to be revised.
Tae-yoon Park; Duck K Choi
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Evolution & development     Volume:  11     ISSN:  1525-142X     ISO Abbreviation:  Evol. Dev.     Publication Date:    2009 Jul-Aug
Date Detail:
Created Date:  2009-07-15     Completed Date:  2009-08-05     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100883432     Medline TA:  Evol Dev     Country:  United States    
Other Details:
Languages:  eng     Pagination:  441-55     Citation Subset:  IM    
School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, Korea.
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MeSH Terms
Arthropods / anatomy & histology,  classification*,  growth & development*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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